Time-shifting for push to talk voice communication systems

ABSTRACT

A network communication device located on a Push To Talk (PTT) communication network and configured to provide time-shifting capabilities to a user of a PTT communication device is disclosed. The network communication device includes a receiver configured to progressively receive time-based media. The network communication device also includes a time-shifting buffer for progressively storing the received time based media as the time-based media is received and a time-shifting buffer controller configured to control the rendering of the time-based media at the PTT device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of pending U.S. application Ser. No.12/336,206, filed Dec. 16, 2008, and entitled “Time-Shifting For Push ToTalk Voice Communication Systems.” U.S. application Ser. No. 12/336,206claims the benefit of priority to U.S. Provisional Patent ApplicationNo. 61/044,272 filed Apr. 11, 2008, entitled “Time-Shifting for VoiceCommunications.” All of the foregoing applications are incorporatedherein by reference in their entirety for all purposes.

BACKGROUND

1. Field of the Invention

The present invention relates to telecommunications, and moreparticularly, to an apparatus for applying time-shifting functionalityto voice communications.

2. Description of Related Art

Voice communication systems consist of one of more “channels.” In thecase of Push To Talk (PTT) systems, such as tactical radios or PTT overCellular (PoC), only a single channel is used whenever someone istransmitting. A user cannot transmit while their device is receiving.These systems are said to be “half-duplex”. The alternative is“full-duplex” systems like landline telephones, cellular telephones, orVoIP systems such as Skype or SIP. Each of these full-duplex systemsuses two channels, one for voice being received and the other for voicebeing transmitted. User communication devices generally “connect” thesechannels, either to a speaker, a microphone, or both, depending on theduplex and current mode of operation.

Many full-duplex telephony systems have some sort of message recordingfacility for unanswered calls such as voicemail. If an incoming callgoes unanswered, it is redirected to a voicemail system. When the callerfinishes the message, the recipient is alerted and may listen to themessage. Various options exist for message delivery beyond dialing intothe voicemail system, such as email or “visual voicemail”, but thesedelivery schemes all require the entire message to be left before therecipient can listen to the message.

Many home telephones have answering machine systems that record missedcalls. They differ from voicemail in that the caller's voice is oftenplayed through a speaker on the answering machine while the message isbeing recorded. The called party can pick up the phone while the calleris leaving a message. If this occurs with most answering machines, therecording of the message stops while the parties engage in a telephoneconversation. With other answering machines, however, the liveconversation will be recorded unless the called party manually stops therecording. In either recording situation, there is no way for the calledparty to review the recorded message until after the recording hasstopped. There is no way for the recipient to review any portion of therecorded message other than the current point of the conversation whilethe conversation is ongoing and is being recorded. Only after theconversation has concluded and the parties have hung up or the recipienthas manually stopped the recording can the recipient go back and reviewthe recorded message or conversation.

Some more recent call management systems provide a “virtual answeringmachine”, allowing callers to leave a message in a voicemail system,while giving called users the ability to hear the message as it is beingleft. The actual answering “machine” is typically a voicemail-styleserver, operated by the telephony service provider. Virtual answeringmachine systems differ from standard voice mail systems in that thecalled party may use either their phone or a computer to listen tomessages as they are being left. Similar to an answering machine asdescribed in the preceding paragraph, however, the called party can onlylisten at the current point of the message as it is being left. There isnot way to review previous portions of the message before the message isleft in its entirety and the caller hangs up.

Certain mobile phone handsets have been equipped with an “answeringmachine” feature inside the handset itself and that behaves similarly toa landline answering machine as described above. With these answeringmachines, callers may leave a voice message, which is recorded directlyon the phone of the recipient. While the answering machine functionalityhas been integrated into the phone, all of the limitations of answeringmachines, as discussed above, are still present.

With current PTT systems, incoming audio is played on the device as itis received. If the user does not hear the message, for whatever reason,the message is irretrievably lost. Either the sender must resend themessage or the recipient must request the sender to re-transmit message.PTT systems generally do not have any sort of “missed message” recordingcapability.

Other forms of PTT messaging systems exist that are purely message basedand are never live. See for example U.S. Pat. No. 7,403,775 and U.S.Publications 2005/0221819 and 2005/0202807.

A problem with all the above-mentioned systems is that there is no wayfor: (i) a recipient of a message to review the message while it isbeing left; (ii) review received messages at an arbitrary time afterreceipt in a time-shifted or messaging mode; or (iii) seamlesslytransition the exchange of messages between a sender and a recipientbetween the time-shifted mode and a real-time mode.

SUMMARY OF THE INVENTION

A network communication device located on a Push To Talk (PTT)communication network and configured to provide time-shiftingcapabilities to a user of a PTT communication device. The networkcommunication device includes a receiver configured to progressivelyreceive time-based media. The network communication device also includesa time-shifting buffer for progressively storing the received time basedmedia as the time-based media is received and a time-shifting buffercontroller configured to control the rendering of the time-based mediaat the PTT device. In response to a control signal received from the PTTdevice of the user, the time-based media is rendered at the PTTcommunication device either (i) in a near real-time mode as thetime-based media is progressively received at the network communicationdevice and progressively transmitted to the PTT device or (ii) at anarbitrary later time after the storage of the time-based media in thetime-shifting buffer by retrieving the time-based media from thetime-shifting buffer at the arbitrary later time and transmitting theretrieved time-based media to the PTT communication device. In variousembodiments, the user of the PTT device is provided a number ofrendering options, including play the time-based media, pausing thetime-based media as it is being rendered, jump backward to reviewprevious time-based media, jump to the most current time-based media,play the time-based media either faster or slower than it was originallyencoded and catch up to live.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, whichillustrate specific embodiments of the present invention.

FIG. 1 illustrates a block diagram of a Store and Stream (SaS) module(i.e., a time-shifting buffer) of the present invention.

FIGS. 2A through 2E are a series of flow diagrams illustrating a storeand stream function of the communication and management system of theinvention.

FIG. 3 is a block diagram of the SaS module embedded in a VoIP client inaccordance with the present invention.

FIG. 4 is block diagram of the SaS module embedded in a Push To Talk(PTT) client according to the present invention.

FIG. 5 is a block diagram of the SaS module embedded in a mobile phonewith PPT over cellular capabilities according to the present invention.

FIG. 6 is a block diagram of the SaS module embedded in a legacytelephone according to the present invention.

FIG. 7 is a diagram illustrating a full duplex conversation with the SaSmodule for the participants located on the network between user devicesaccording to the present invention.

FIG. 8 is a diagram of illustrating a PTT transmission with the SaSmodule located on the network.

It should be noted that like reference numbers refer to like elements inthe figures.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

The present invention will now be described in detail with reference tovarious embodiments thereof as illustrated in the accompanying drawings.In the following description, specific details are set forth in order toprovide a thorough understanding of the present invention. It will beapparent, however, to one skilled in the art, that the present inventionmay be practiced without using some of the implementation details setforth herein. It should also be understood that well known operationshave not been described in detail in order to not unnecessarily obscurethe present invention.

In U.S. application Ser. No. 12/028,400, filed on Feb. 8, 2008 andentitled “Telecommunication and Multimedia Management Method andApparatus,” an improved voice and other media communication andmanagement system and method is disclosed. The system and methodprovides one or more of the following features and functions: (i)enabling users to participate in multiple conversation types, includinglive phone calls, conference calls, voice messaging, consecutive orsimultaneous communications; (ii) enabling users to review the messagesof conversations in either a live mode or a time-shifted mode (voicemessaging); (iii) enabling users to seamlessly transition a conversationbetween a synchronous “live” mode and a time shifted mode; (iv) enablingusers to participate in conversations without waiting for a connectionto be established with another participant or the network. Thisattribute allows users to begin conversations, participate inconversations, and review previously received time-shifted messages ofconversations even when there is no network available, when the networkis of poor quality, or other participants are unavailable; (v) enablingthe system to save media payload data at the sender and, after networktransmission, saving the media payload data at all receivers; (vi)enabling the system to organize messages by threading them sequentiallyinto semantically meaningful conversations in which each message can beidentified and tied to a given participant in a given conversation;(vii) enabling users to manage each conversation with a set of usercontrolled functions, such as reviewing “live”, pausing or time shiftingthe conversation until it is convenient to review, replaying in avariety of modes (e.g., playing faster, catching up to live, jump to thehead of the conversation) and methods for managing conversations(archiving, tagging, searching, and retrieving from archives); (viii)enabling the system to manage and share presence data with allconversation participants, including online status, intentions withrespect to reviewing any given message in either the live ortime-shifted mode, current attention to messages, rendering methods, andnetwork conditions between the sender and receiver; (iix) enabling usersto manage multiple conversations at the same time, where either (a) oneconversation is current and all others are paused; (b) multipleconversations are rendered consecutively, such as but not limited totactical communications; or (c) multiple conversations are active andsimultaneously rendered, such as in a stock exchange or trading floorenvironment; (ix) enabling users to store all conversations, and ifdesired, persistently archive them in a tangible medium, providing anasset that can be organized indexed, searched, transcribed, translatedand/or reviewed as needed; (x) enabling the system to provide real timecall functionality using a best-efforts mode of message delivery at arate “good enough” for rendering as soon as possible (similar to UDP),and the guaranteed eventual delivery of exact copies of the messages astransmitted by requesting retransmission of any missing or defectivedata from the originally saved perfect copy (similar to TCP); and (xi)enabling the system to optimize the utilization of network bandwidth bymaking tradeoffs between timeliness and media quality, using thepresence and intentions of the recipient(s) (i.e., to either review themedia in real-time or in a time-shifted mode), as well as measures ofnetwork latency, network degradation, packet loss or damage, and/orcurrent bandwidth conditions. For more details on the Telecommunicationand Multimedia Management Method and Apparatus, see the above-mentionedU.S. application Ser. No. 12/028,400, incorporated by reference hereinfor all purposes.

One of the main components in the aforementioned system is a Store andStream (SaS) module. Wit the present invention, one or more SaSmodule(s) may be provided on end-user communication devices and/or atvarious nodes or hops on a circuit-based network, such as the PublicSwitched Telephone Network (PSTN), analog voice networks, cellularnetworks, Push To Talk (PTT) networks, or any other circuit type basednetwork. One or more SaS module(s) may also be provided on end-userdevices and/or nodes of a packet-based network or a VoIP network orother network system designed to replicate the functionality oftelephone or PTT radio systems using packets. It should be understoodthat the term “network” should therefore be broadly construed to includeany circuit-based or packet based network and should not be construed aslimiting in any way.

Time-based media is any media that changes meaningfully with respect totime. Voice or video clips are both considered time-based media becausethey both substantively change as time passes. By way of comparison, astill photo is generally not considered time-based media because it isstatic and does not change with the passage of time.

In embodiments where the SaS module is embedded in an end-usercommunication device, such as a mobile or cellular phone, handset,radio, PTT communication device, etc., the SaS module acts as atime-shifting buffer between the existing audio/voice hardware on thedevice (i.e., a microphone or speaker) and the transmitting andreceiving hardware on the device, such as a radio transceiver. Any mediaeither generated at or received at the end-user device is stored in atime-based format in the time-shifting buffer in a time-based format.

In embodiments where the SaS module is deployed on a server on thenetwork, in what is hereafter referred to as a network communicationdevice, then the time-shifting buffer functionality is located on thenetwork, between the transmitting and receiving end-user communicationdevices. Transmissions between the two communication devices are storedin a time-based format in the time-shifting buffer on the network.

In yet other embodiments, SaS modules may be provided at both end usercommunication devices and on the network in one or more networkcommunication devices. With this arrangement, the transmissions arestored both on the SaS enabled end user devices and on the one or morenetwork communication devices on the network.

The Store and Stream module persistently stores time-based media in thetime-based format as the media is received. With embodiments where theSaS module is located on a network communication device, the time-basedmedia is stored as it is received from one or more end-usercommunication devices as the one or more end-user communication devicessend transmissions back and forth over the network. With embodimentswhere the SaS module is on the end-user communication device itself, thereceived media that is stored includes both time-based media created byor otherwise originating at the end-user communication device itself andtime-based media received over the network from others who have sentmessages.

With standard full-duplex telephone calls, regardless if over legacyphone systems, cellular, wireless, or VoIP, a number of new functionsare provided by the storage of voice as time-based media in the SaSmodule. Foremost, a user may participate in an ongoing exchange ofmessages in either (i) a “live” near real-time mode, similar to aconventional phone call where spoken words are sent back and forthbetween the participants, (ii) a time-shifted mode, where the user hearsa message at some point “behind” the live point, along with the abilityto catch up to the live point by playing the intervening message ormessages faster or directly skipping over messages to arrive at the livepoint; or (iii) seamlessly transition between the real-time mode and thetime-shifted mode.

If an incoming message is missed, the SaS module records the messagefrom the sender. By default, missed messages would be in a time-shiftedstate. As missed messages are received, they are queued in storage forlater review by the recipient. Alternatively, if a called party ispresent when a message is received, the called party may chose to engagein the conversation in the real-time mode or review the message at anarbitrary time later in the time-shifted mode. In addition, since themessage is being recorded in the SaS module, the recipient also has theoption of reviewing any portion of the message as it is being receivedwith a number of playback controls, described in more detail below.

Storing the media at the SaS module provides a number of functionspreviously not available on communication systems: (i) it enables usersto leave a message for another party, even when the sender and/or therecipient has poorly functioning or otherwise unavailable networkconnectivity; (ii) the recipient has the ability to pause, replay,fast-forward, and catch-up-to-live with an ongoing exchange of messagesbetween two or more parties such as during a conversation; (iii) theability to retrieve and review previously sent, stored and archivedmessages; (iii) locally generated messages can be mixed as appropriateto create overlapping messages (generated by the normal overlap ofmultiple speakers during a conversation); (iv) enables the transcriptionor translation of voice media into either text or other languages; and(v) it enables users with several rendering options, including reviewingmessages faster or slower, for example.

When listening to messages at some time after the messages have beenreceived in the time-shifted mode, the SaS module provides the user withthe ability to speed up the review of the recorded messages at arendering rate faster than the rate the messages were originallyencoded. This allows for more rapid reviewing of older content and alsoallows users to “catch up” to the live point of a conversation,seamlessly transitioning from the review of previously received andstored media of the conversation with new media as it is being received,hereafter referred to as “catch-up-to-live”.

With half-duplex or Push-To-Talk (PTT) systems, either on a tacticalradio style device or using PTT over Cellular, the SaS module providesnew functionality, including the ability to communicate in either thereal-time mode or time-shifted mode, and the ability to seamlesslytransition between the two modes, similar to that described above withregard to full duplex communication systems. In addition, PTT users willhave the ability to skip forward and backward on a per-message basis.For each message, the user has the option of implementing all theabove-listed playback features (e.g., play faster, play slower, catch upto live, etc.). With a SaS module equipped PTT system, incoming messagesmay optionally be played as they are being received. All receivedmessages, however, are stored for review at an arbitrary later timedefined by the recipient. If a user is reviewing an old message while anew message is received, an indication may be provided. Users have theoption of reviewing other messages simultaneously with the arrival ofnew messages or serializing the review of incoming messages. Users canalso replay messages that were missed without asking the sending partyto retransmit. Further, the SaS module enables a PTT user to set a “donot disturb” mode of interaction where incoming transmissions that arerecorded and queued for recipient are not played through the speaker.The time-indexing, recording, and the rendering of messages in thetime-shifted mode can also apply to any locally generated transmissions.In this manner, a PTT user can review their message contributions, inaddition to any received messages, of an ongoing conversation.

With a SaS module embedded in the device of a sending user, the delayimposed on the user by the network for call setup and “volley” times arereduced. A sending user may begin speaking immediately while the SaSmodule time-indexes and stores the message as time-based media. As thestorage is occurring, the sending device carries out the usual networknegotiation and setup processes. When a circuit or network connection isestablished, the SaS module will send the message from storage startingfrom the beginning of the message. The typical sequence of a callerwaiting for a connection to be established and the phone to ring beforespeaking is thus eliminated.

Referring to FIG. 1, a block diagram of the SaS module 24 according toone embodiment of the present invention is shown. The main function ofthe SaS module 24 is that it acts as a time-shifting buffer forcommunication devices connected to circuit-based or packet basednetworks that replicate the functionality of telephone or PTT radiosystems such as VoIP. The components of the SaS module 24 are describedin detail below. It should be noted that in the embodiment illustratedin FIG. 1, the SaS module 24 is intended for use in an end-usercommunication device. In embodiments where the SaS module is located ata node on the network in a network communication device, some of thefunctionality illustrated in FIG. 1 is not required, as pointed out inthe discussion below.

The Persistent Infinite Message Buffer (PIMB)

The Persistent Infinite Message Buffer or PIMB 30 stores or recordstime-based media in a time-indexed format and provides a system for theretrieval of the media. In one embodiment, the media in the PIMB 30 isarbitrarily persistent, meaning it is available virtually forever or atleast until it is purposely deleted or deleted in accordance with apredefined retention policy. This persistence is in comparison toexisting jitter buffer technology that discards media as soon as it isrendered. Various retention rates and strategies may be employed to makeeffective use of storage resources. Many possible implementations existfor the physical storage implementation of the PIMB 30, including, butnot limited to: ROM, RAM, volatile memory, non-volatile memory, Flashmemory, hard drives, optical media, or some combination thereof. In onespecific embodiment, the PIMB 30 may be implemented using a small andrelatively fast RAM cache memory coupled with a hard drive forpersistent storage. The PIMB 30 is also “infinite in size, meaning theamount of media that can be stored is not inherently limited. As thephysical storage capacity of the PIMB 30 is exceeded, the media ismaintained in secondary or archival storage for later retrieval.

In various embodiments, the archival storage may be either local orremote. In embodiments where the SaS module 24 is a node on a network,the archival storage may be located at the same node or at another nodeon the network. In embodiments where the SaS module 24 is located on aend-user communication device, the archival storage may be either localat the device or at a remote location accessible over the network. Apredefined criteria or a replacement algorithm, such asleast-recently-used, or first-in-last-out, is used to control the actualmedia stored in the PIMB 30 or archived at any point in time. The PIMB30 further provides the attributes of file system storage and the randomaccess attributes of a database. Any number of conversations ormessages, regardless of their duration, may be stored and laterretrieved for review.

In addition, the meta-data associated with messages, such as itsoriginator and its length, may be also stored in the PIMB 30. Inalternative embodiments, the media and other data can be stored for adesignated period of time (e.g. 30 days). Once the age of the mediaexceeds the designated period, the media is discarded. In anotherembodiment, media may be discarded based on the sender and/or therecipient of the message, or the topic of the message. In yet otherembodiments, certain media may be marked for transience, meaning themessages will not be stored in the PIMB 30 beyond the requirements forimmediate rendering.

The PIMB Writer

The PIMB writer 28 writes data to the PIMB 30 for two basic purposes.The PIMB writer 28 writes media into the PIMB 30 derived from mediareceived from a media-capturing device, such as a microphone or videocamera (“Encode Receive”). The PIMB writer 28 also writes mediacontained in messages received over the network from others into thePIMB 30 (“Net Receive”). The Encode Receive and Net Receive functionsare described in more detail below.

1. Encode Receive

For capturing locally generated media, the PIMB writer 28 includesEncoder Receiver 28 a and a Media Storer 28 b. When a User speaks intothe microphone for example, the hardware 34 receives the raw audiosignals and provides them to the Encoder Receiver 28 a, which encodesthe voice into electrical signals, for example in digital form. TheMedia Store 28 b time-indexes the digital signals and stores the signalsas time-based media in the PIMB 30. Other types of time-based media,such as video, is processed and stored in a similar manner. The EncodeReceive function is typically implemented only on an end usercommunication device. In embodiments where the SaS module 24 is locatedon the network, the Encode Receive functionality may not be needed orimplemented.

2. Net Receive

For storing the media of messages received over the network into thePIMB 30, the Net Receive function of PIMB writer 28 includes a NetworkReceiver 28 c, a Media Bufferer 28 d, and a Media Storer 28 e. TheNetwork Receiver 28 c receives the time-based media of messages over thenetwork. The Media Bufferer 28 d buffers the incoming signals asnecessary. The Media Storer 28 e time-indexes and stores the time-basedmedia in the PIMB 30. The Net Receive function would typically beimplemented in a SaS module 24 located on both an end-user communicationdevice and in a network communication device located at a node on thenetwork.

The PIMB Reader

The PIMB reader 26 reads data from the PIMB 30 for two basic purposes.The PIMB reader 26 accesses the PIMB 30 when a message is to be rendered(“Render”) for the user. Data is also read from the PIMB 30 when mediais to be transmitted (“Transmit”) over the network. The Render andTransmit functions are described below.

1. Render

For the rendering of messages, the PIMB reader 26 includes a MediaRetriever 26 f, a Media Mixer 26 g and a Media Decoder 26 h. The MediaRetriever 26 f retrieves the media selected for rendering from the PIMB30. If the selected media of two or more messages overlap by time-index,the Mixer 26 g mixes the overlapping retrieved media. The Media Decoder26 h decodes or converts the media (in either mixed or non-mixed form)into signals in a form suitable for the hardware driver 34. The hardware34 then drives a speaker or video display, creating audio and/or videosignals. The Render function is typically implemented only on an enduser communication device. In embodiments where the SaS module 24 islocated on the network in a network communication device, the Renderfunctionality may not be needed or implemented.

2. Transmit

To transmit messages over the network, the PIMB Reader 26 includes aMedia Retriever 26 i, and a Transmitter 26 j. The Retriever 26 i selectsthe media from the PIMB 30 for transmission and the Transmitter 26 jtransmits the selected media. Where the SaS module 24 is located on anend-user communication device, the selected media may be either mediapreviously stored in the PIMB 30 or media that is currently beingcreated locally for transmission to a recipient over the network. Invarious embodiments, the currently created media may be stored in thePIMB either (i) just before transmission; (ii) just after transmission,or (iii) or at substantially the same as the media is transmitted. Withall three embodiments, any delays associated with storage andtransmission are sufficiently small so that the recipient may perceive a“live” experience if rendering the media in the near real-time mode.

With embodiment where the SaS module 24 is located on a networkcommunication device on the network, the media selected for transmissionis media that was either previously stored in the PIMB 30 or media thatis being progressively received from a sender for transmission to arecipient. With the former, the media is typically being retrieved fromthe PIMB 30 when the recipient wishes to review a previously receivedand stored message in the time-shifted mode. With the latter, therecipient is reviewing the transmission in the real-time mode, meaningthe network communication device is progressively receiving,progressively storing in the time-indexed format in the PIMB 30, andprogressively transmitting the message to the recipient as the media isbeing received.

Interface Circuit

The interface circuit 40 is responsible for providing an interfacebetween the SaS module 24 and the underlying application module of anend-user communication device. For example, with a VoIP clientcommunication device, the interface circuit 40 provides the interfacebetween the SaS module 24 and the underlying VoIP application of thedevice. For a PTT radio, the interface circuit 40 provides the interfacebetween the SaS module 24 and the PTT radio application module on thedevice. With a mobile phone with PTT capabilities over cellular or astandard legacy telephone phone, the interface circuit provides aninterface between the PTT and underlying cellular radio module orstandard telephone module of the devices respectively. In each case, theunderlying application module is the hardware and/or softwareresponsible for implementing the VoIP, PPT, and legacy phonefunctionality of the end-user communication device. A networkcommunication device with an SaS module 24 would typically not includean interface circuit 40, unless the network communication deviceimplemented some of the functionality described above.

Controller

A controller 46 is provided to allow a user to interact or control theoperation of time-shifting buffer capabilities of the SaS module 24through the controller interface 48. Through the controller 46, a usercan implement a host of functions such as the selection of a messageamong a plurality of messages or the selection of a number of availablerendering options, such as: (i) pausing a live a message, (ii) jumpbackward to review a previous message or messages, (iii) jump to thehead (i.e. “live”) or the most current message among an exchange ofmessages between participants, (iv) play recorded messages faster, (v)play recorded messages slower, and (vi) catching up to live by reviewingthe stored messages of an exchange of messages at a rate faster relativeto the rate the voice media was originally encoded and stored andseamlessly merging into the current live message.

In embodiments where the SaS module 24 is provided on an end-usercommunication device, the controller 46 is designed to interface withany number of user input control or selection features provided on theend-user communication device itself. Control or selection features,such as a touch screen graphical user interface, touch input controls,knobs, a keyboard, slide bars, etc. may be provided enter rendering andother control commands to the SaS module 24 through the controller 46.

In embodiments where the SaS module 24 is provided at a networkcommunication device, the controller 46 is configured to receive controlsignals over the network. For example, a user of an end-usercommunication device may remotely operate the controller 46 on the SaSmodule 24 on the network through various control functions usingDual-Tone Multi-Frequency tones, Short Message Service (SMS) messages,or some other out-of-band signaling mechanism. With PTT applications forexample, the controller 46 enables a user to remotely interact with theSaS module 24 to implement a wide variety of new functions. For example,PTT users can control the SaS module 24 to skip forward and backward ona per-message basis as well as the rendering controls described abovewithin each message (e.g., play faster, play slower, etc.). Incomingmessages may still be played as they are received, but all receivedmessages will be stored for later review at an arbitrary later timedefined by the receiving user. If a user is reviewing an old message,while a new message is received, an indication or flag may be providedthrough the controller 46. By manipulating the controller 46, users havethe option of reviewing other messages simultaneously with the arrivalof new messages or serializing the review of incoming messages. Userscan also replay messages that were missed without asking the sendingparty to retransmit. In yet another embodiment, a “do not disturb” modecan be set where incoming transmissions are recorded and queued forlater review without being immediately played or rendered. Thecontroller 46 also allows a sender to review their sent messages, inaddition to any received messages.

Operation Flow Diagrams

Referring to FIGS. 2A through 2E, a series of flow diagrams are providedto illustrate the operation of the SaS module 24 on end-usertransmitting and receiving communication devices. FIG. 2A shows thesequence of operation of the SaS module when a user transmits messagesto a recipient. FIGS. 2B and 2C illustrate the operation of the PIMBwriter 28 and PIMB Reader 26 during transmission. FIGS. 2D and 2Eillustrate the operation of the PIMB Writer 28 and PIMB Reader 26 whenthe SaS module 24 receives a message. The flow charts below aredescribed in the context of voice media. It should be understood thatthe flow charts operate in a similar manner for other types oftime-based media, such as video, positional or GPS data, or other sensordata (e.g., temperature, pressure, etc.).

In FIG. 2A, a user creates messages to be transmitted by speaking intothe microphone of their end-user communication device. With the EncodeReceive function, the voice signals of the message are encoded as theuser speaks by the PIMB Writer 28 (box 130), which converts the voiceinto electrical signals and stores the electrical signals in the PIMB 30(box 132) as Media in a time-indexed format. With the Transmit function,the PIMB Reader 26 transmits the message to the recipient participant(s)over the network 133. At the receiving SaS module 24, the Net Receivefunction of the PIMB Writer 28 receives the message (box 136) and storesthe message as time-based media into the PIMB 30 on the receive SaSmodule 24. The Render function of the PIMB reader 26 on the receive siderenders the time-based media from the PIMB 30 into a medium suitable forhuman consumption, such as voice or video. Each of these steps aredescribed in more detail below with respect to FIGS. 2B through 2E.

In FIG. 2B, the sequence of the Encoder Receive function performed bythe PIMB Writer 28 (step 130 of FIG. 2A) is provided in detail. In theinitial step 130 ₁, the transmitting user originates the voice signalsor a message to be transmitted, by for example, speaking into amicrophone. In the next step 130 ₂, the Encode Receiver 28 aprogressively encodes the voice signals as they are being created. TheMedia Storer 28 b associates a time-index with the encoded signals asthe person is speaking (step 130 ₃) and then progressively stores themedia in the PIMB 30 (step 132 ₄) in a time-indexed format.

In FIG. 2C, the sequence of the Transmit function performed by the PIMBReader 26 (step 134 of FIG. 2A) on the sending SaS module 24 is providedin detail. In the initial step 134 ₁, the media to be transmitted isselected by the Media Retriever 26 i. If the selected media is the mediathat is currently being created on the end user device, then theTransmitter 26 j progressively transmits the media in variousembodiments either just before, just after or at substantially the sametime as the media is stored in the PIMB 30 by the Encode Receivefunction. Regardless of the embodiment, the media is transmitted withouta perceptible delay. As a result, the recipient(s) may optionally renderthe media in the real-time mode. Alternatively, the user may selectmedia for transmission over the network from the PIMB 30 (step 134 ₃)that was previously stored. For example, a user may select an oldmessage and transmit it over the network. In this latter case, theTransmitter 26 j retrieves the media from the PIMB starting at theselected point and progressively transmits the media from storage.

In FIG. 2D, the sequence for the Net Receive function (step 136 of FIG.2A) of the PIMB Writer 28 of the receive SaS module 24 is illustrated.In the initial step 136 ₁, the Network Receiver 28 c progressivelyreceives the time-based media of the message over the network. Asnecessary the incoming media is buffered by the Media Bufferer 28 d. TheMedia Storer 28 e progressively associates the time-index for thereceived media (step 136 ₂) and then progressively stores media in thePIMB 30 (step 136 ₃) in the time-indexed format.

In FIG. 2E, the sequence for the Render function of the PIMB Reader 26(box 140 of FIG. 2A) on the receive SaS module 24 is illustrated. In theinitial step 140 ₁, the media (e.g., a message) at a point in time isselected. The Media Retriever 26 f then progressively retrieves themedia from the PIMB 30 starting at the selected point of time (step 140₂). The retrieved time-based media is then progressively mixed by theMedia Mixer 26 g if appropriate (step 140 ₃). In the next step, theDecoder 26 h progressively decodes either the mixed or non-mixed media(step 140 ₄) into electrical signals suitable for the hardware driver34, which drives a media-generating device such as a speaker or videodisplay (step 140 ₅) to generate audio or video.

In the real-time mode, the media selected for rendering is the mediabeing progressively received. In various embodiments of the Net Receiveand Render functions, an incoming message may be time-indexed and storedin the PIMB either just before, just after or at substantially the sametime the media is being rendered at the end-user device of therecipient. In either case, the delay associated with storing the mediais very small. As a result, the recipient may render the media live inthe real-time mode. In the time-shifted mode, the media is selected froma previous point in time, retrieved from the PIMB 30, and rendered fromthe selected point forward.

In the context of the present application, the term progressive orprogressively is intended to be broadly construed and generally mean thecontinuous processing of a data stream based on availability of thedata. For example as a person speaks, their voice is continuouslyencoded, stored, and transmitted, so long as the voice media is beingcreated. When the person pauses or stops speaking, there is no voicemedia to continuously process. But when the person resumes speakingagain, the progressive processing and transmission of the voice mediaresumes. On the receive side, the media is also progressive processed(i.e. stored) in any recipient SaS module, either on the network in anetwork communication device or at a recipient ender user communicationdevice. Further if a recipient has indicated they would like to reviewthe media in the real-time mode, then any intermediate networkcommunication device will continuously or progressively transmit mediato the recipient, so long as the media is available. The recipientend-user communication device also continually renders the media as itis progressively received, so long as the media is available.

The flow diagrams 2A through 2E describe the operation of the SaS module24 on an end-user communication device as noted above. The operation ofthe SaS module 24 on the network in a network communication deviceoperates essentially the same, except for two notable exceptions. Sincemedia is typically not created or rendered on the network, the EncodeReceive (FIG. 2B) or Render (FIG. 2E) functions are typically notimplemented. Instead, only the Transmit (FIG. 2C) and Net Receive (FIG.2D) functions are required.

Referring to FIG. 3, a block diagram of the SaS module embedded in aVoIP client in accordance with one embodiment of the present inventionis shown. In this disclosure, “VoIP” should be understood as a systemthat provides full-duplex voice and/or video communication using the IPprotocol. Example of such systems includes SIP, RTP, Skype, H.323, MGCP,IAX2, etc. In this embodiment, the VoIP client 50 includes a networkinterface 52 to connect the client 50 to a network 54, a VoIPapplication module 56 for providing the VoIP functionality, a speaker57, a microphone 58, a VoIP controller 60, the SaS module 24, and thecontroller 46.

The VoIP application module 56 controls the VoIP functionality of theclient 50 as is well known in the art. The SaS module 24, which isprovided between the network 54 and the speaker 57 and microphone 58 onthe client device 50, provides the time shifting buffer and SaSfunctionality, as described above, directly on the device. The operationof the SaS module 24 is controlled through the controller 46, also asdescribed above. The VoIP controller 60 controls the standard operationof the VoIP application module 56, as is well known in the art, throughthe SaS module 24. The standard VoIP controls for call initiation andmanagement are routed through the SaS module 24 first before they aresent to the VoIP application module 56 so that the SaS module 24 canallocate necessary resources for the activities of the VoIP application.With this arrangement, a user of the device sends VoIP related requeststo SaS module 24, which in turn, relays them to VoIP application module56.

Referring to FIG. 4, a block diagram of the SaS module embedded in aPush To Talk (PTT) client 70 according another embodiment of the presentinvention is shown. In this embodiment, the PTT client 70 includes aradio antenna 72 to connect the client 70 to a PTT radio network (notillustrated), a PTT radio application module 74 for providing the PTTfunctionality, a speaker 76, a microphone 78, a PTT radio controller 79,the SaS module 24, and the controller 46.

The PTT radio application module 74 controls the PTT functionality ofthe client 70 as is well known in the art. The SaS module 24, which isprovided between the PTT radio network (not illustrated) through theantenna 72 and the speaker 76 and microphone 78 on the client device 70,provides the time shifting buffer and SaS functionality, as describedabove, directly on the device. The operation of the SaS module 24 iscontrolled through controller 46, also as described above. The PTT radiocontroller 79 controls the standard operation of the PTT radioapplication module 74, as is well known in the art, through the SaSmodule 24.

Referring to FIG. 5, a block diagram of the SaS module embedded in amobile phone with PPT over cellular capabilities according to anotherembodiment of the present invention is shown. In this embodiment, themobile phone with PPT over cellular client 80 includes a radio antenna82 to connect the client 80 to a cellular network (not illustrated), aPTT and cellular radio module 84 for providing standard cellular and PTTfunctionality, a speaker 86, a microphone 88, a cellular phone/PTTcontroller 89, the SaS module 24, and the SaS controller 46.

The PTT and cellular radio module 84 controls PTT and full-duplex voicefunctionality of the client 80 as is well known in the art. The SaSmodule 24, which is provided between the cellular radio network (notillustrated) through the antenna 82 and the speaker 86 and microphone 88on the client device 80, provides the time shifting buffer and SaSfunctionality, as described above, directly on the device. The operationof the SaS module 24 is controlled through controller 46, also asdescribed above. The cellular phone/PTT radio controller 89 controls thestandard operation of the PTT and cellular radio application module 84through the SaS module 24.

In another embodiment, the SaS module 24 may be provided on a standardmobile phone without the PTT capability and which operates over acellular network. Such an embodiment would be very similar to the client80 as illustrated in FIG. 5, except the module 84 and the controller 89would not have PTT functionality or PTT controls respectively.

Referring to FIG. 6, a block diagram of the SaS module embedded in alegacy telephone according to yet another embodiment of the presentinvention is shown. In this embodiment, the telephone client 90 includesa legacy telephone transceiver 92 to connect the client 90 to a legacytelephone network (not illustrated), a legacy or standard telephonemodule 94 for providing standard telephone functionality, a speaker 96,a microphone 98, a telephone keypad 99, the SaS module 24, and the SaScontroller 46.

The legacy telephone module 94 controls PTT and full-duplex voicefunctionality of the client 90 as is well known in the art. The SaSmodule 24, which is provided between the legacy telephone network (notillustrated) through the transceiver 92 and the speaker 96 andmicrophone 98 on the client device 90, provides the time shifting bufferand SaS functionality, as described above, directly on the device. Theoperation of the SaS module 24 is controlled through controller 46, alsoas described above. The telephone keypad 99 controls the standardoperation of the legacy telephone module 84 through the SaS module 24.

In each of the embodiments described above in FIGS. 3 through 6, the SaSmodule 24 is provided on the client. But as previously noted, the SaSmodule 24 may be provided on the network, providing legacy land-linephones, mobile phones, PTT radios, and PTT enabled mobile phones withSaS functionality.

Referring to FIG. 7, a diagram illustrating a full-duplex conversationwhere the SaS modules 24 for the participants are located on the networkis shown. In this embodiment, two non-SaS enabled end-user devices A andB are engaged in a full-duplex conversation and two networkcommunication devices 100, each including an SaS module 24, are providedon the network for user A and B respectively. With this arrangement,media transmitted by user A to user B is transmitted using a firstchannel. A second channel is used for transmissions from user B to userA. Any transmissions on the first and second channels are stored in theSaS modules 24 of the two network communication devices 100respectively. FIG. 8 is a diagram illustrating a half-duplex PTT systemwith two network communication devices 100, each including an SaS module24, for storing the transmissions from end user device A to end userdevice B (e.g., conventional PTT devices).

With the embodiments shown in both FIGS. 7 and 8, user B controls itsrespective SaS module 24 through various control functions using DTMFtones, SMS messages, or some other out-of-band signaling mechanism. Thecontroller 46 of the SaS module 24 corresponding to user B, in responseto the control signals received from the communication device of user B,is configured to control the rendering of the time-based media from userA at the communication device of user B in either the near real-time ortime-shifted modes.

In the near real-time mode, as the time-based media is progressivelyreceived at the SaS module 24 from the communication device A, it isprogressively stored in the PIMB 30 and progressively transmitted to thecommunication device B for immediate rendering. As a result, user B hasa “real-time” experience when reviewing or rendering the media.

On the other hand in the time-shifted mode, the transmission is notimmediately rendered at device B as it is being transmitted by device A.For example, if user B is not available, or intentionally wishes not toreview a transmission from user A in real-time, then the transmission isreceived and stored in the PIMB 30 of the SaS module 24 corresponding touser B, but is not progressively forwarded to the device of user B. Atsome later time arbitrary defined by user B, the media of the missedtransmission may be reviewed.

To review the media in the time-shifted mode, user B generates controlsignals requesting the message. In response, the SaS module 24 retrievesthe time-based media of the message from the PIMB 30 and progressivelytransmits the retrieved time-based media to the communication device ofuser B for rendering. In addition, user B may further generate a numberof control signals to select any number of rendering options besidessimply playing the time-based media, such as pausing time-based media asit is being rendered, jump backward to review previous time-based media,jump to the most current time-based media, play the time-based mediaeither faster or slower than it was originally encoded and catch up tolive.

User B may also seamlessly transition between the near-real-time andtime-shifted modes. For example, user B may pause or stop the renderingof a message from user A in the real-time mode. In this situation, userB may subsequently review the message at an arbitrary later time in thetime-shifted mode. Alternatively, user B may be reviewing an old messagefrom user A when a new message arrives. If this occurs, user B may stopthe review of the old message and immediate transition to the review ofthe new message as the media arrives in the real-time mode.Alternatively, user B can implement the catch up to live feature,speeding up the rendering of the old media until caught up with the newmedia as it progressively arrives over the network. In either case, userB seamlessly transitions from the time-shifted mode to the nearreal-time mode.

Although not described in detail herein, user A may review transmissionsfrom user B in either the real-time or time-shifted modes, and with allthe same rendering controls, in a similar manner as described above. Inan alternative embodiment, a single network communication device 100 maysupport both end user devices A and B for the embodiments shown in FIG.7 or 8 respectively. With this embodiment, although there is only onenetwork communication device 100, at least a dedicated PIMB wouldtypically be provided for each user A and B respectively. In yet otherembodiments, each communication device 100 may each support multipleusers besides A and B in either a half-duplex or full-duplexarrangement. In either case, again at least a dedicated PIMB wouldtypically be provided the for each user respectively. In situationswhere SaS modules support multiple users, transmit and receive functionsmay be shared. But each user would ideally have a separate PIMB or adedicated portion of a larger PIMB. Also with the embodiments shown inFIGS. 7 and 8, either or both user devices A and B may have their ownSaS modules 24.

Although the above description was generally provided in the context ofvoice media, it should be understood that all types of time-based mediacould be processed in a similar manner. SaS modules 24, regardless oftheir location, can process other types of time-based media, such asother audio content besides voice, video, GPS or positional data, orsensor data such as time, temperature, pressure, etc.

Although many of the components and processes are described above in thesingular for convenience, it will be appreciated by one of skill in theart that multiple components and repeated processes can also be used topractice the techniques of the present invention. Further, while theinvention has been particularly shown and described with reference tospecific embodiments thereof, it will be understood by those skilled inthe art that changes in the form and details of the disclosedembodiments may be made without departing from the spirit or scope ofthe invention. It is therefore intended that the invention beinterpreted to include all variations and equivalents that fall withinthe true spirit and scope of the present invention.

What is claimed is:
 1. A method performed on a communication network,the method comprising: progressively storing voice media received at anode on a communication network during PTT transmissions exchangedbetween a first PTT communication device and a second PTT communicationdevice over the communication network as the voice media isprogressively received at the node; progressively transmitting the voicemedia received at the node during the PTT transmissions exchangedbetween the first and second PTT communication devices: (a) from thefirst PTT communication device to the second PTT communication device asthe voice media is progressively received and stored at the node whenthe second PTT communication device is available on the network; and (b)from the second PTT communication device to the first PTT communicationdevice as the voice media is progressively stored at the node when thefirst PTT communication device is available on the network;progressively transmitting the voice media received from the first PTTcommunication device out of storage on the node to the second PTTcommunication device when: (i) the second PTT communication device isunavailable on the network when the voice media is received and storedat the node; and (ii) in response to a request from the second PTTcommunication device after the second PTT communication device becomesavailable on the network; progressively transmitting the voice mediareceived from the second PTT communication device out of storage on thenode to the first PTT communication device when: (iii) the first PTTcommunication device is unavailable on the network when the voice mediais received and stored at the node; and (iv) in response to a requestfrom the first PTT communication device after the first PTTcommunication device becomes available on the network; and providing anapplication that is embedded in a non-transient computer readable mediumto the first PTT communication device, the application configured to:(1) enable the progressive storage on the first PTT communication devicethe voice media that is created on the first PTT communication device;(2) enable the progressive transmission of the voice media created onthe first PTT communication device as the voice media is created andprogressively stored on the first PTT communication device if a networkconnection is established for the first PTT communication device whenthe voice media is created on the first PTT communication device; and(3) enable the progressive transmission of the voice media created onthe first PTT communication device out of storage on the first PTTcommunication device after the first PTT communication deviceestablishes the network connection if the network connection was notestablished for the first PTT communication device when the voice mediawas created on the first PTT communication device.
 2. The method ofclaim 1, wherein progressively storing the voice media at the nodefurther comprises progressively and persistently storing the voice mediaat the node, wherein persistently stored means for a time period beyondwhat is needed to deliver the voice media to the first PTT communicationdevice or the second PTT communication device respectively.
 3. Themethod of claim 1, wherein progressively storing the voice media at thenode further comprises progressively storing the voice media in atime-indexed format so that the voice media can be retrieved fromstorage in time-order.
 4. The method of claim 1, wherein the applicationis further configured to enable progressive storage of the voice mediaprogressively received over the communication network from the secondPTT communication device as the voice media is progressively receivedover the communication network.
 5. The method of claim 1, wherein theapplication includes a rendering module configured to enable selectiverendering of the voice media received over the communication networkfrom the second PTT communication device both: (i) in near real-time byprogressively rendering the voice media as the voice media is received;and (ii) at an arbitrary later time by rendering the received voicemedia out of storage on the first PTT communication device.
 6. Themethod of claim 5, wherein the rendering module provides one or more ofthe following rendering options: play, pause, jump backward, jump to themost current voice media, play faster, play, and catch up to live. 7.The method of claim 1, further comprising supporting half-duplexcommunication over the communication network between the first PTTcommunication device and the second PTT communication.
 8. The method ofclaim 1, further comprising supporting time-shifted communication overthe communication network by enabling the first PTT communication deviceand the second PTT communication device to render the voice mediaexchanged between the two PTT communication devices some time after theexchanged media was transmitted.
 9. The method of claim 8, whereinsupporting time-shifted communication further comprises enabling usersof the two PTT communication devices to render the exchanged voice mediaout of storage some time after the exchanged media was transmitted bythe two PTT communication devices respectively.
 10. The method of claim1, wherein the first PTT communication device comprises one of thefollowing: a computer, a PTT radio, a mobile phone, a telephone.
 11. Themethod of claim 1, wherein, besides voice media, the media exchangedbetween the two PTT communication devices and stored at the nodecomprises one or more of the following: (i) video media; (ii) imagemedia; (iii) GPS or positional data; (iv) sensor data; or (v) textmedia.
 12. The method of claim 1, wherein the first PTT communicationdevice is a communication device that transmits voice media created onthe communication device in response to the activation of a PTT functionlocated on the communication device.
 13. The method of claim 1, whereinthe voice media that is progressively transmitted by either of the twoPTT communication devices is in a PTT format and is progressivelyreceived by the other of the two communication devices in the PTTformat.
 14. A communication system comprising: a node located on acommunication network, the node configured to progressively store PTTvoice media transmissions between a first PTT communication device and asecond PTT communication device exchanged over the communication networkas the voice media is progressively received at the node, the nodefurther configured to: progressively transmit the voice media receivedat the node during the PTT transmissions exchanged between the first andthe second PTT communication devices (a) from the first PTTcommunication device to the second PTT communication device as the voicemedia is progressively received and stored at the node when the secondPTT communication device is available on the network; and (b) from thesecond PTT communication device to the first PTT communication device asthe voice media is progressively received and stored at the node whenthe first PTT communication device is available on the network;progressively transmit the voice media received from the first PTTcommunication device out of storage on the node to the second PTTcommunication device when: (i) the second PTT communication device isunavailable on the network when the voice media is received and storedat the node; and (ii) in response to a request from the second PTTcommunication device after the second PTT communication device becomesavailable on the network; and progressively transmit the voice mediareceived from the second PTT communication device out of storage on thenode to the first PTT communication device when: (iii) the first PTTcommunication device is unavailable on the network when the voice mediais received and stored at the node; and (iv) in response to a requestfrom the first PTT communication device after the first PTTcommunication device becomes available on the network; and providing anapplication that is embedded in a non-transient computer readable mediumto the first PTT communication device, the application configured to:(1) enable the progressive storage on the first PTT communication devicethe voice media that is created on the first PTT communication device;(2) enable the progressive transmission of the voice media created onthe first PTT communication device as the voice media is created andprogressively stored on the first PTT communication device if a networkconnection is established for the first PTT communication device whenthe voice media is created on the first PTT communication device; and(3) enable the progressive transmission of the voice media created onthe first PTT communication device out of storage on the first PTTcommunication device after the first PTT communication deviceestablishes the network connection if the network connection was notestablished for the first PTT communication device when the voice mediawas created on the first PTT communication device.
 15. The system ofclaim 14, wherein the progressive storage of the voice media at the nodefurther comprises progressively and persistently storing the voice mediaat the node, wherein persistently stored means for a time period beyondwhat is needed to deliver the voice media to the first PTT communicationdevice or the second PTT communication device respectively.
 16. Thesystem of claim 14, wherein the progressive storage of the voice mediaat the node further comprises progressively storing the voice media in atime-indexed format so that the voice media can be retrieved fromstorage in time-order.
 17. The system of claim 14, wherein theapplication is further configured to enable progressive storage of thevoice media progressively received over the communication network fromthe second PTT communication device as the voice media is progressivelyreceived over the communication network.
 18. The system of claim 14,wherein the application includes a rendering module configured to enableselective rendering of the voice media received over the communicationnetwork from the second PTT communication device either: (i) in nearreal-time by progressively rendering the voice media as the voice mediais received; and (ii) at an arbitrary later time by rendering thereceived voice media out of storage on the first PTT communicationdevice.
 19. The system of claim 18, wherein the rendering moduleprovides one or more of the following rendering options: play, pause,jump backward, jump to the most current voice media, play faster, play,and catch up to live.
 20. The system of claim 14, wherein the system isfurther configured to support half-duplex communication over thecommunication network between the first PTT communication device and thesecond PTT communication device.
 21. The system of claim 14, furthercomprising supporting time-shifted communication over the communicationnetwork by enabling the first PTT communication device and the secondPTT communication device to render the voice media exchanged between thetwo PTT communication devices some time after the exchanged media wastransmitted.
 22. The system of claim 21, wherein supporting time-shiftedcommunication further comprises enabling users of the two PTTcommunication devices to render the exchanged voice media out of storagesome time after the exchanged media was transmitted by the two PTTcommunication devices respectively.
 23. The system of claim 14, whereinthe first PTT communication device comprises one of the following: acomputer, a PTT radio, a mobile phone, a telephone.
 24. The system ofclaim 14, wherein, besides voice media, the media exchanged between thetwo PTT communication devices and stored at the node comprises one ormore of the following: (i) video media; (ii) image media; (iii) GPS orpositional data; (iv) sensor data; or (v) text media.
 25. The system ofclaim 14, wherein the first PTT communication device is a communicationdevice that transmits voice media created on the communication device inresponse to the activation of a PTT function located on thecommunication device.
 26. The system of claim 14, wherein the voicemedia that is progressively transmitted by either of the two PTTcommunication devices is in a PTT format and is progressively receivedby the other of the two communication devices in the PTT format.